Blowing an 18-point, second-quarter lead in Game 5 has done nothing to dim the Knicks’ extreme confidence in sending this Eastern Conference Finals back to Indiana for a Game 7 Sunday.

From one end of the Purchase gym, Patrick Ewing predicted the Knicks will win Game 6 tonight at the Garden. And from another corner, Chris Childs was back in the “guarantee” business. The Knicks trail the Pacers 3-2 in the best-of-seven and are back tonight at the Garden, where the Pacers are 0-4 this season.

“We’re going to win [tonight] and come back Sunday and try to win that also,” said Ewing, whose Game 5 return did not spark the Knicks to victory. “This team thrives on adversity. That’s the way it has been since I’ve been here. I guess it’s just going to have to be one of those type of series for us.”

Childs “guaranteed” the Game 6 win vs. the Heat in the second round and backed up his words with heroic performances in the final two contests, particularly Game 7. Yesterday, asked if he had another prediction for this Game 6, Childs didn’t disappoint:

“I guarantee we’ll go back to Indiana,” Childs said. “I guarantee we’re going back. I know we’re going to play better and come out and play the best game we’ve played all year.”

Childs, in particular, played one of his worst games all year and he’s had some stinkers. Childs shot 1 of 7 – 1 of 4 from 3-point land. Childs launched two airballs to lead the Knick shooting collapse as their 18-point lead early in the second quarter evaporated.

Latrell Sprewell, who seemed noticeably impaired on his broken left foot in the 88-79 Game 5 loss, stopped short of assuring a seventh game. “Me personally, I don’t want to guarantee anything,” Sprewell said. “It just gives the other team added motivation to play harder. Being confident is one thing. The guys on this team are confident and they really do believe we’re going to win.”

“Confidence is only an issue if you do the right things within the scheme of what you’re trying to do,” said Allan Houston, who scored 25 points. “Obviously if you don’t rebound or don’t defend, confidence doesn’t mean anything.”

Even coming off their Conseco Fieldhouse choke job Wednesday, the Knicks have reason to feel good about tonight, despite their spate of injuries – of which Sprewell’s appears the most damaging. The Pacers have truly been a horror show at the Garden this season. But Ewing (tendinitis in right foot), Sprewell, Marcus Camby (sprained right knee) and Larry Johnson (plantar fasciitis) are banged up.

“There’s a certain amount of discouragement not being able to play their best at this point of the year,” Jeff Van Gundy said. “I would say one of our problems as a team is durability and it has been. Maybe it’s unusual for most teams [to have this many injuries] but one of our weaknesses is we’re not a durable group.”

But the Knicks are desperate now and they won’t be holding anything back. “Mentally we know this could be our last practice, last shootaround, last game,” said Sprewell, who scored 10 points in Game 5. “That’s definitely in the back of our minds. It’s definitely a motivating factor.”

The Knicks faced elimination in the second round against Pat Riley, down 3-2, but fought back heroically from an 18-point second-quarter deficit in Game 6 and eventually won the series in seven on the road. “We’re back there again,” Sprewell said. “We didn’t intend to be in this position but the bottom line is we are. We’ll see if we can respond like we did in the Miami series.”

The Knicks watched the Game 5 film yesterday for more than an hour and then went through a brief walkthrough. Van Gundy thought the Knicks’ 32-17 lead in the first quarter was an optical illusion after the Knicks made 12 of 19 shots, including their first eight.

“All we did well in the first quarter is we made perimeter shots,” Van Gundy said. “We did nothing better in the first quarter in any other way except we made shots. We didn’t guard better, we didn’t rebound better. We didn’t make hustle plays better. It’s fool’s gold to think you’re going to just shoot your way to a win. All we did was stand on the perimeter and fire up jumpers.”

Hammered on the offensive glass, the Knicks got blitzed 23-3 across the second period’s final 10 minutes in one of the worst collapses in a big spot in Knick history. The Knicks trailed 42-40 at halftime and never led in the second half.

“The biggest thing was our inability to handle one big run,” Van Gundy said. “We just let it go, go , go. We never had the mental toughness to gather ourselves in the second quarter or halftime to re-energize ourselves. Even when we were within seven with seven minutes to go we didn’t have the look like we were going to win.”